Bump json from 2.6.3 to 2.9.1

Bumps [json](https://github.com/ruby/json) from 2.6.3 to 2.9.1.
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.6.3...v2.9.1)

---
updated-dependencies:
- dependency-name: json
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -33,7 +33,7 @@ GEM
     http-cookie (1.0.5)
       domain_name (~> 0.5)
     http-form_data (2.3.0)
-    json (2.6.3)
+    json (2.9.1)
     jwt (2.7.1)
     llhttp-ffi (0.4.0)
       ffi-compiler (~> 1.0)